Rear air brake chambers must be free to breathe through the pushrod opening and the 2 lower position vent holes in the spring brake chamber near the clamping flange. Make sure these openings are clear. The 2 uppermost vent holes should be plugged.

Leakage Test

1. Block the wheels.
2. Start the engine.
3. Charge the air system to the air compressor governor valve cut-out point.
4. Stop the engine.
5. Have an assistant apply and hold the brake pedal.
6. Apply a soap solution around the air brake chamber clamp and the breather holes.
7. Verify that no bubbles appear.

•	Lightly tap on the clamp and tighten the clamp bolts if bubbles appear.

•	Overhaul or replace the rear air brake chamber if the bubbles continue. Refer to Front Air Brake Chamber Overhaul or Rear Air Brake Chamber Overhaul and Caging the Rear Air Brake Chamber .

8. Set the parking brake.
9. Remove the wheel blocks.